target-i386: block migration and savevm if invariant tsc is exposed

Invariant TSC documentation mentions that "invariant TSC will run at a
constant rate in all ACPI P-, C-. and T-states".

This is not the case if migration to a host with different TSC frequency
is allowed, or if savevm is performed. So block migration/savevm.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
[AF+mtosatti: Updated error message]
Signed-off-by: Andreas Färber <afaerber@suse.de>

target-i386/cpu-qom.h

@@ -121,7 +121,7 @@ static inline X86CPU *x86_env_get_cpu(CPUX86State *env)
 #define ENV_OFFSET offsetof(X86CPU, env)
 
 #ifndef CONFIG_USER_ONLY
-extern const struct VMStateDescription vmstate_x86_cpu;
+extern struct VMStateDescription vmstate_x86_cpu;
 #endif
 
 /**

target-i386/kvm.c

@@ -35,6 +35,8 @@
 #include "exec/ioport.h"
 #include <asm/hyperv.h>
 #include "hw/pci/pci.h"
+#include "migration/migration.h"
+#include "qapi/qmp/qerror.h"
 
 //#define DEBUG_KVM
 
@@ -448,6 +450,8 @@ static bool hyperv_enabled(X86CPU *cpu)
             cpu->hyperv_relaxed_timing);
 }
 
+static Error *invtsc_mig_blocker;
+
 #define KVM_MAX_CPUID_ENTRIES  100
 
 int kvm_arch_init_vcpu(CPUState *cs)
@@ -705,6 +709,17 @@ int kvm_arch_init_vcpu(CPUState *cs)
                                   !!(c->ecx & CPUID_EXT_SMX);
     }
 
+    c = cpuid_find_entry(&cpuid_data.cpuid, 0x80000007, 0);
+    if (c && (c->edx & 1<<8) && invtsc_mig_blocker == NULL) {
+        /* for migration */
+        error_setg(&invtsc_mig_blocker,
+                   "State blocked by non-migratable CPU device"
+                   " (invtsc flag)");
+        migrate_add_blocker(invtsc_mig_blocker);
+        /* for savevm */
+        vmstate_x86_cpu.unmigratable = 1;
+    }
+
     cpuid_data.cpuid.padding = 0;
     r = kvm_vcpu_ioctl(cs, KVM_SET_CPUID2, &cpuid_data);
     if (r) {

target-i386/machine.c

@@ -603,7 +603,7 @@ static const VMStateDescription vmstate_msr_hyperv_time = {
     }
 };
 
-const VMStateDescription vmstate_x86_cpu = {
+VMStateDescription vmstate_x86_cpu = {
     .name = "cpu",
     .version_id = 12,
     .minimum_version_id = 3,